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  #11  
Old 05-31-2019, 10:32 PM
Marc Bourget Marc Bourget is offline
 
Join Date: Apr 2009
Location: Stockton, California
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I remember reading about a pair of doors in the upper plenum that were hinged. On the ground they would open, but in flight the dynamic pressure would find them closed.

Never saw a picture, but by this reference maybe someone else has photos?
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  #12  
Old 06-01-2019, 12:11 AM
crabandy crabandy is offline
 
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Location: Ottawa, Ks
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I think Iíve had my ďlight bulbĒ moment, now just time to implement it.
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  #13  
Old 06-01-2019, 12:23 AM
crabandy crabandy is offline
 
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Quote:
Originally Posted by BobTurner View Post
I think this idea has some merit for increasing the battery cooling, via convection, when on the ground. I'm not so sure about in-flight. If the area above the new opening has a higher pressure than the exit area from the cowl (between the exhausts), then you will get some cool air over the battery - but at the expense of higher pressure at the exit, which may mean reduced cylinder cooling/higher CHTs. OTOH if the new opening area has a lower pressure than the normal exit area, then you will get additional flow up and out, helping cylinder cooling - but at the cost of running warm air over the battery. I don't know how to find out without actually testing in flight.
Bob, Thx for the thoughts.
Convection cooling on the ground agreed!

As far as in flight Iím still assuming a lot, Iím not planning on drawing air in from the oil door. Im assuming that the area around the oil door is close to atmospheric pressure (same as he lower exit) and will be additional exit area. Lower cowling pressures of 1.5-2.0 inches of H2O at climb speeds should push air out both exits Iím thinking. Either way once I have air moving through the cowling at climb speeds the lower cowling temps drop 50+ degrees from the stagnant ground ops.
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  #14  
Old 06-01-2019, 08:48 AM
rocketman1988 rocketman1988 is online now
 
Join Date: Jun 2010
Location: Sunman, IN
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Many years ago, I recall seeing a guy that made automatic doors using the thermostat from an auto engine. It was a pretty neat idea...
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Bob
Aerospace Engineer '88

RV-10
Structure - 90% Done
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  #15  
Old 06-18-2019, 12:15 AM
crabandy crabandy is offline
 
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I want the oil door/cowl flap to open inward, I must still be able to access the oil filler tube and cowling pins. The stock placement of the oil door isn't quite optimum for opening inward, clearance with the oil filler tube and engine mount aren't enough. If I can figure out the geometry of hinging the door at an angle I may be able to create a larger oil door/cowl flap than a horizontal hinge line, we'll see. Either way I need a smooth clean slate on the inside of the cowl.

I ground the rivets off the existing oil door hinge and strike plate and chiseled them off the cowling.



Roughened things by sanding both sides, the drill motor sand paper flap attatchment is my sledgehammer approach to sanding. I used it to initially smooth out the epoxy ridges from the hinge and strike plate.





I couldn't quite find that "just right" material I was looking for to act as a backer-board for the outer cowling. The plastic cutting board sheets from Wal-mart have gotten thinner and a little too floppy, I ended up using 1/8" Acrylic Sheet from the hardware store that was a little too stiff.



A hairdryer to warm it up helped it conform a little, clecos to hold it in place.

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Last edited by crabandy : 06-18-2019 at 12:42 AM.
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  #16  
Old 06-18-2019, 12:40 AM
crabandy crabandy is offline
 
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I made several templates with 2 mil plastic and a sharpie.





I'm not in love with my replacement scale (up to 50lbs is too big), my first el-cheapo light weight scale worked better on the lighter weights. For most of my layups I mix the epoxy in 20-50 gram batches in tiny cups, saves on waste and exotherming. I do like putting the scale in a gallon plastic baggie and once I can no longer read the display I replace the baggie.



I mixed a soupy batch of epoxy/flox/micro and spread it into the existing exterior flange of the oil door opening, set in a 2 ply sheet of 9 oz cloth and clecoed on the acrylic sheet. Fiberglass was wet-out between 2 mil plastic and cut out reference the previous templates with the fabric pizza cutter.



4 more plys of 9 oz cloth filling the opening on the oil door and another fillet of epoxy/flox/micro around the edges. It was topped with scraps overlaping the oil door gaps and finally peel-ply.



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  #17  
Old 06-18-2019, 08:58 PM
crabandy crabandy is offline
 
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The acrylic sheet cleco'd to the cowl did a pretty nice job of fairing the new glass to the existing glass, as exepected I have a dozen or so "worm holes" to fill between the flange and new glass/epoxy filler slurry.



I verified the oil dipstick clearance.



I made a cardboard template and taped it on the hinge line to check for clearances for opening the door to the inside.



The oil filler cap and engine mount limit the door size/shape when hinging horizontally on the lower side.





I made a plastic template of the oil door for the cowling cutout and making fiberglass pieces for the oil door, it's approximately 31 sq inches compared to the stock 27 sq inch oil door. I estimated my stock cowling exit in the low 50 sq inches which I've since shrunk to about 35 sq inches. The oil door/cowl flap should increase my total exit area to 60+ square inches. Again the in-flight benefits would be a bonus, I'm mostly counting on convection cooling on the ground.



The inside of the cowling still had protruding ridges from the stock cowling opening, I added fiberglass strips around my proposed opening, I'll have to sand most of it back off but it should leave me with a smooth surface requiring a smidge of filler to mate the oil door/cowl flap too.

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Last edited by crabandy : 06-18-2019 at 09:11 PM.
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  #18  
Old 06-20-2019, 10:47 PM
crabandy crabandy is offline
 
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I faired in the new glass with a little micro than cut the new hole. I beveled the inside edges for a radiused lip for the oil door to seal against from the inside.



I didn't preplan well enough and had to shim a piece of plastic cutting board in where the acrylic was too small. I wanted a tight fit without tape lines so I waxed the cowling and shot 3 coats of PVA.



I started with 2 plys of 8.9 oz glass cut to fit the opening, I then used a slightly undersized piece of Lantor Soric core material. I've found the soric doesn't make a nice finished edge so I used a filet of epoxy/flox around the edges of the soric.



A couple more plys of 8.9 oz glass to join it all together and make a flange to seal against the cowling.



Stinks I didn't use a large enough piece of acrylic, I'm sure it'll take a couple extra hours to fair in the little overlap of the plastic cutting board. From the top side You can see the filet of epoxy flox around the edges of the undersized Soric.

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Last edited by crabandy : 06-20-2019 at 10:54 PM.
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  #19  
Old 06-24-2019, 01:38 AM
crabandy crabandy is offline
 
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The new oil door/cowl flap was TIGHT in the cowling, a smidge of epoxy/flox had flowed from the door between the cowling and the acrylic. Even after sanding the new door flush with the cowling it was staying in place, I really started to have doubts that the wax and PVA didn't keep the epoxy from bonding to the cowl on the thin edge and thought I might have to cut it out. In the end I was able to slowly pry it out, I had rounded the edges of the cowling too much and it created a concave joint on the new door that kept it in place.

The new door cleaned up and in place on the airplane.



View from the inside, I really should've made it 1/8" smaller all the way around as I only have 3/32" clearance from the dipstick and engine mount. I can still sand the flange down a tad for more clearance.







On the positive side of things the new door offers a lot more room for:
-installing the firewall hinge pins
-oil filler/dipstick
-battery charging port
-engine sump heater port



I've got the model of my linear servo picked out, just have to scratch my head over the geometry and stroke length.
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Last edited by crabandy : 06-24-2019 at 01:41 AM.
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  #20  
Old 06-25-2019, 12:56 AM
crabandy crabandy is offline
 
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I decided on the 100MM stroke, 64:1 gear ratio P16-S linear actuator from Actuonix. The P series actuators are more robust than the L series, I would like 125mm stroke but 100 should work.

https://www.actuonix.com/P16-S-Linea...or-p/p16-s.htm

I roughly calculated 31 sq in of oil door area, I currently have 1-2 inches of H2O of lower cowling pressure for most flight speeds. Calculating for 3 inches of H2O (.11psi) is 3.41 lbs of force holding the oil door closed.

I chose the 64:1 gearing not for the 90N (20ish lbs) lifting but the speed is slower, Iím also going to be operating it at an angle (still unknown) that will require more force. Iím hoping for the advertised longer life especially operating in 170-200+ *F. Most every micro servo I looked at was rated at 5 lbs and 50*C (122*F), the P series is still only rated for 50*C.
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